> From: Jason Gunthorpe <jgg@xxxxxxxxxx> > Sent: Tuesday, October 20, 2020 10:05 PM > To: Liu, Yi L <yi.l.liu@xxxxxxxxx> > > On Tue, Oct 20, 2020 at 02:00:31PM +0000, Liu, Yi L wrote: > > > From: Jason Gunthorpe <jgg@xxxxxxxxxx> > > > Sent: Tuesday, October 20, 2020 9:55 PM > > > > > > On Tue, Oct 20, 2020 at 09:40:14AM +0000, Liu, Yi L wrote: > > > > > > > > See previous discussion with Kevin. If I understand correctly, > > > > > you expect a > > > shared > > > > > L2 table if vDPA and VFIO device are using the same PASID. > > > > > > > > L2 table sharing is not mandatory. The mapping is the same, but no > > > > need to assume L2 tables are shared. Especially for VFIO/vDPA > > > > devices. Even within a passthru framework, like VFIO, if the > > > > attributes of backend IOMMU are not the same, the L2 page table are not > shared, but the mapping is the same. > > > > > > I think not being able to share the PASID shows exactly why this > > > VFIO centric approach is bad. > > > > no, I didn't say PASID is not sharable. My point is sharing L2 page > > table is not mandatory. > > IMHO a PASID should be 1:1 with a page table, what does it even mean to share > a PASID but have different page tables? PASID is actually 1:1 with an address space. Not really needs to be 1:1 with page table. :-) Regards, Yi Liu > Jason
